An algebra interface for describing algebraic data types.
An algebra interface for describing algebraic data types. Such descriptions
can be interpreted to produce a JSON schema of the data type, a JSON encoder,
a JSON decoder, etc.
A description contains the fields of a case class and their type, and the
constructor names of a sealed trait.
For instance, consider the following record type:
caseclass User(name: String, age: Int)
Its description is the following:
object User {
implicitval schema: JsonSchema[User] = (
field[String]("name") zip
field[Int]("age")
).invmap((User.apply _).tupled)(Function.unlift(User.unapply))
}
The description says that the record type has two fields, the first one has type String and is
named “name”, and the second one has type Int and name “age”.
To describe sum types you have to explicitly “tag” each alternative:
sealedtrait Shape
caseclass Circle(radius: Double) extends Shape
caseclass Rectangle(width: Double, height: Double) extends Shape
object Shape {
implicitval schema: JsonSchema[Shape] = {
val circleSchema = field[Double]("radius").invmap(Circle)(Function.unlift(Circle.unapply))
val rectangleSchema = (
field[Double]("width") zip
field[Double]("height")
).invmap((Rectangle.apply _).tupled)(Function.unlift(Rectangle.unapply))
(circleSchema.tagged("Circle") orElse rectangleSchema.tagged("Rectangle"))
.invmap[Shape] {
case Left(circle) => circle
case Right(rect) => rect
} {
c: Circle => Left(c)
r: Rectangle => Right(r)
}
}
}
An algebra interface for describing algebraic data types. Such descriptions can be interpreted to produce a JSON schema of the data type, a JSON encoder, a JSON decoder, etc.
A description contains the fields of a case class and their type, and the constructor names of a sealed trait.
For instance, consider the following record type:
Its description is the following:
The description says that the record type has two fields, the first one has type
String
and is named “name”, and the second one has typeInt
and name “age”.To describe sum types you have to explicitly “tag” each alternative: